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     "text": [
      "aaaaa\n"
     ]
    }
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   "source": [
    "x=5\n",
    "x=\"a\"*x\n",
    "print(x)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ff499751-42af-4a47-896b-244f39f75f10",
   "metadata": {},
   "source": [
    "# 一级标题\n",
    "\n",
    "## 二级标题\n",
    "\n",
    "### 三级标题\n",
    "\n",
    "这是一段普通文本，**这是粗体文本**，*这是斜体文本*，***这是粗斜体文本***。\n",
    "\n",
    "这是一个链接：[豆包编程助手](https://www.doubao.com)\n",
    "\n",
    "这是一个列表：\n",
    "- 项目1\n",
    "- 项目2\n",
    "  - 子项目2.1\n",
    "  - 子项目2.2\n",
    "- 项目3\n",
    "\n",
    "这是一个有序列表：\n",
    "1. 第一步\n",
    "2. 第二步\n",
    "3. 第三步\n",
    "\n",
    "这是一个代码块：\n",
    "```python\n",
    "def hello_world():\n",
    "    print(\"Hello, World!\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "53fc4464-420c-4187-a83b-76b35036ad75",
   "metadata": {},
   "source": [
    "<!DOCTYPE html>\n",
    "<html>\n",
    "<body>\n",
    "\n",
    "<header>\n",
    "  <h1>简易网页示例</h1>\n",
    "  <nav>\n",
    "    <a href=\"#\">首页</a> |\n",
    "    <a href=\"#\">产品</a> |\n",
    "    <a href=\"#\">关于</a> |\n",
    "    <a href=\"#\">联系</a>\n",
    "  </nav>\n",
    "</header>\n",
    "\n",
    "<main>\n",
    "  <section>\n",
    "    <h2>欢迎访问</h2>\n",
    "    <p>这是一个示例页面，展示了基本的 HTML 元素。</p>\n",
    "  </section>\n",
    "\n",
    "  <section>\n",
    "    <h2>特性列表</h2>\n",
    "    <ul>\n",
    "      <li>响应式设计</li>\n",
    "      <li>语义化结构</li>\n",
    "      <li>无障碍支持</li>\n",
    "    </ul>\n",
    "  </section>\n",
    "\n",
    "  <section>\n",
    "    <h2>产品展示</h2>\n",
    "    <div>\n",
    "      <h3>产品一</h3>\n",
    "      <img src=\"https://picsum.photos/300/200?random=1\" alt=\"产品图片\">\n",
    "      <p>描述产品一的特点和优势。</p>\n",
    "    </div>\n",
    "    <div>\n",
    "      <h3>产品二</h3>\n",
    "      <img src=\"https://picsum.photos/300/200?random=2\" alt=\"产品图片\">\n",
    "      <p>描述产品二的特点和优势。</p>\n",
    "    </div>\n",
    "  </section>\n",
    "\n",
    "  <section>\n",
    "    <h2>联系我们</h2>\n",
    "    <form>\n",
    "      <label>姓名: <input type=\"text\" required></label><br>\n",
    "      <label>邮箱: <input type=\"email\" required></label><br>\n",
    "      <label>留言: <textarea rows=\"3\" required></textarea></label><br>\n",
    "      <button type=\"submit\">提交</button>\n",
    "    </form>\n",
    "  </section>\n",
    "</main>\n",
    "\n",
    "<footer>\n",
    "  <p>© 2025 示例版权所有</p>\n",
    "</footer>\n",
    "\n",
    "</body>\n",
    "</html>"
   ]
  },
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   "execution_count": null,
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   "metadata": {},
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   "source": []
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    "$$\n",
    "\\int_{a}^{b} f(x) \\, dx = F(b) - F(a)\n",
    "$$\n",
    "\n",
    "行内公式示例：$ \\nabla \\cdot \\vec{E} = \\frac{\\rho}{\\varepsilon_0} $\n",
    "\n",
    "二元二次方程的求根公式：\n",
    "$$\n",
    "x = \\frac{-b \\pm \\sqrt{b^2 - 4ac}}{2a}\n",
    "$$\n",
    "\n",
    "矩阵乘法示例：\n",
    "$$\n",
    "\\begin{bmatrix}\n",
    "a & b \\\\\n",
    "c & d\n",
    "\\end{bmatrix}\n",
    "\\times\n",
    "\\begin{bmatrix}\n",
    "e & f \\\\\n",
    "g & h\n",
    "\\end{bmatrix}\n",
    "=\n",
    "\\begin{bmatrix}\n",
    "ae+bg & af+bh \\\\\n",
    "ce+dg & cf+dh\n",
    "\\end{bmatrix}\n",
    "$$\n",
    "\n",
    "概率密度函数的性质：\n",
    "$$\n",
    "\\int_{-\\infty}^{\\infty} f(x) \\, dx = 1 \\quad \\text{且} \\quad f(x) \\geq 0 \\quad \\forall x \\in \\mathbb{R}\n",
    "$$"
   ]
  }
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